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Psoriatic keratinocytes show reduced STAT-1α and IRF-1 activation in response to IFN-γ
S152
ESDR I JSID I SID Abstracts
0910
0907
PSORIATICKERATINOCYTES SHOW REDUCED STAT-la AND IRF-1 ACTIVATION
AUTOCR,NE GROWTH FACTORS FOR EPIDERMOID CARCINOMA CELLS. & Meaner. U. Zinmfer. C. Hofmann and I. Norpauer, Department of Dermatology, Umversity c#Fmiburg, Germany. The CXC-chemokkms Grea and ieterleukin-8 (IL-Q stimulate the growh of melanoma cells and the ehemaaxis of neutmphils via the IL-8 receptor 0 (ILSRP). Recently high CXC-ehemokine immunoreac&y was detected in the lexms of pmlifemtive skin dwxden such as kerateaeanthoma and sqeanwus cell carcinoma. To &cidete the functional relevanceofthese fmdingsthe expreexm Grcu, IL-8 and the IL-SRP as well as their funetmnal i~nolwmmt in the proliferation response were aealysed in normal keratinozytes @+K) end in the tmnsfonned keratinccyte (TK) cell hem HaCaT, KB and A431. Semiquantitative RT-PCR and ELISA revealed vay low ecmstitutive mRNA exprerrim and protein secretion of both CXC-ehemokines in NK, whereas IO- to 100~fold higher levels were de&xl in TK. Flow cytemetric measuranents showed high expreasim ofIL-8Rb in TK, but no expression in NK. ‘Ihis tinding was corroborated by receptor mRNA assamat wkh semiquantitativs RT-PCR and analysis of II&Q promoter activity by CAT-assay showing markedly increased saady-state levels of IL-SRp mRNA as well es trenscription aaivity in TK, but not hr NK. Pmbferatmn of TK, but nd of NK, could be induced by CXC-chemekines. Canstitutive molifbration OCTK could be inibii bv neetralizin~ antibodies against the CXC&es or against IL-8RP. These studies indxate that comtitetwe b-anscripttcmally~gul& IL-SRp expissioo induces a CXC-ehemokine autwiee loop in TK supportinggrowth. mis finding eught o&r new implicatiaw for the dwelcpmaa oftherapeutic appreaches in tmnsfbrmed kemtinocyter.
IN RESPONSE
TO 1FN-y. M&any
Jackson.
Sarah
EM.
Howle*.
Rl$;ar;r:,
Weller, Elizabeth Sobln*, John A.A. Hunter. and Roddie C K I Departments of Dermatology and *Pathology. Unlverstty of’ Edinburgh: Edinburgh, Scotland. Psorlasls Is a ChronlC lnnammatory dermatosls characterlsed by hyperprollferatlve keratlnocytes (KC) which fall to terminally differentlate. The lesions are lnflnrated by IFN-y-secreting mononuclear cells which help maintain the pSOr,atlc phenotype. In normal KC, IFN-y Is a potent lnhlbiior of prollferat&I and modulator of squamous dlfferentlatlon. Slgnalllng via the IFNy receptor. and subsequent gene Induction, Involves actlvatlon of the transcrlptlOn faCtOrsSTAT-laand IRF-I, cuhnlnating In the blndlng of IRF-1 to the prOmOterS of IFNy-lnduclble genes. We sought to determlne whether there Is a defect In the response of psorlatlc KC to FN-y, which could explain the KC hyperproHferatlon In the IFNy-rich plaque. Cultures of normal adult and psorlotlc KC were established and stimulated with IFN?. Transcrtptlon fact01 aCtlVation was quantltoted by gel mobility shfft assay and autoradlography. In both normal and psorlEltlc KC, STAT-la actlvatlon was maximal 15M min. after stknulatlon; the kinetics were slmlkx. however, the pSorlatlC KC showed Smclller Increases In STAT-ICI actlvatlon after 10 min. (p=O.o37) and 15. 30, and 60 mk-!. (pe0.M. n=5). At 60 mln, STAT-la aCtlvatlOn increased by 71.fold in normal KC compared with 31-fold In p.XX,atlC KC. The decreased magnitude of STAT-la actlvatlon was followed by decreased IRF-1 actlvatlon, maximal after J-Bh. Normal KC showed a 6fold Induction. whereas IRF-1 acttvatlon in psorlotlc cells was only 2.7-fold. This lack of responsiveness to 1FN-y lndtcates a tundamental defect In the growth and differentlatlon control of psorlatlc KC, In the absence of other cell types.
of
0908
0911
GROWTH FACTOR+ (TGF-P) IS NOT INVOLVED IN GROWTH INHIBITION OF HUMAN KERATINOCYTES BY la, 25(OH),D,. A STUDY WITH ADENOVIRAL VECTOR EXPRESSING A TRUNCATED TGF-p TYPE II RECEPTOR (AdexCATpTR). Yasu$hi Hanakawa. Yujj Shirakata. Kensi Yamasaki. Koii Sm Hikaru Ueno’. and Koii Hashimoto. Dept of Dermatology Ehime University School of Medicine,Ehime, Japan, *Dept. of Cardiology Kyushu University School of Medicme, Fukuoka, Japan. la, ‘IT-Dlhydroxyvitamin Da(1a, 25(0H),D& an active form of vitamin D,, inhibits the growth of normal human keratlnocytes (NHK). An involvement of TGF-p, an autocrine growth inhibitor for NHK, is proposed, although it is still controversial because of difficulty to block TGF-p activity in NHK. To solve this problem, we constructed an adenoviral vector (Adex) expressing a truncated TGF-p type II receptor (TBTR) with a dominant negative effect, which blocks TGF-6 slonal transduction. NHK was cultured in serum-free MCDB153 medlbm and DNA synthesis was measured by bromodeoxyuridine Incorporation. A 90 minute infection with AdexCAT@TRat 5 m o i. (multiplicity of InfectIon) induced an expression of TBTR in NHK after 24 h, confirmed by immunoblot and immunostaining, and abolished the growth inhibitory effect on NHK of TGF-61 at 0.1 to 5 ng/ml completely. An addition of 1O-6M of la, 25(OH),Dsto NHK infected with 5 m.o.i of AdexCATbTR and Adex (control vector) reduced DNA synthesis to 59.3% and 62.2% at 6 h, 24.1% and 31.8% at 12 h, respectwely. Since 10, 25(OH),D,inhibits the NHK growth regardless of prevention of TGF-p signal transduction. TGF-P is not involved in the growth InhibItion of NHK by la. 25(0H),Dz
COLLAGENASE-3 (MMP-13) EXPRESSION BY SQUAMOUS CELL CARCINOMA CELLS IS DEPENDENT ON THE ACTIVITY OF p38 MI,TOGEN A;$ATED PROTEIN IUNASE. Nina G~eman*. and Maw Ktih&ri, Depts. of Dermatology and *Gtorhinolaryngology, University of Turku. Finland. ~ollagenase-3 (MMP-13) is a new matrix metallopmteinase (MMF’), which is specifically expressed by transformed keratinccytes, i.e. HaCaT cells and tumor cells of invasive squamous cell carcinomas (SCCs) of the head and neck in culture and in viva. We have elucidated the molecular mechanisms of enhancement of hlMF-13 expression at mRNA and pm&in level by tomor necrosis factor-a (TNF-a) and transforming growth factor+ (TGF-p) in HaCaT cells and in cell lines from cutaneous and oral SCCs. In both HaCaT and SCC cells TNF-a and TGF-!3 rapidly and transiently activate hvo distinct mitogen activated pmtein kinases (MAPKS): extracellolar stimulus-regulated kinase (ERK)l,Z and ~38 MAPK. In addition, TNF-a activates Jun N-terminal k&se. Treatment with SB 203580, a selective inhibitor of ~38 MAPK entirely abrogated the. induction of MMP-13 expression by both TNFa and TGF-fl and also inhibited basal expression of MMP-I3 by HaCaT and SCC cells. In addition, SB 203580 abrogatedthe stimulation of collageruse(MMP-1) expression by TGF-fl and TNF-a and entirely inhibited release of collagenolytic activity to culture media in response to TNF-a and TGF-p. Inhibition of MAPK pathway Raf/MBKl/ERKl,2 by PD 98059, a specific inhibitor of MF,Kl activation also partially prevented stimulation of MMP- 13 expression by TGF-B, but not by TNF-a. These results show that activation of both MM&I3 and MMP-I expression in transformed keratinocytes by TNF-a and TGF-p requires activity of ~38 MAPK, indicating that specific inhibition of this pathway may provide a novel way to combat invasion and metastasis of SCC cells.
0909
0912
TRANSFORMING
ACTIVATION-DEPENDENT
EXPRESSION
MAST
Griitzkau.
CELL LINE,l.
&nnelie
Mtiller.
University,
Balm,
Vascular
Departments
lization
growth
factor
VECiF,m,
VEGF,,sor
VEGF,m,
of these isoforms
VEGFII,,
HUMAN
Clinic, Humboldt
VEG&,and
VEGFII,.
lysis of the conditioned
the protem level. In summary, source of the strong heparin
leukemic
Vay
recently,
mast cell line-l expressed
was a&wed by sequence
thus study provides
VEGFzw m these cells is dependent
that have been stu-
VEGF at the mRNA
of stimulated
bmdlng
spli-
isoforms,
VECiFzos mRNA
could
HMC-1
on appropriate
by RT-PCR.
while
by HMCThe amph-
Western
cells confumed
evidence
de nova ex-
(HMC-I),
and released
analysis.
growth factor VEGF,,
we could
and at the protein
for the first time the stimulated
was verified
medium
The &forms
level is unknown.
of VEGF*,x mRNA
expected
alternative
homodimeric
the kidney and the heart, the exact loa-
VEGF,89 were constitutively
detection
of the product
in the human
undergoes
While VEGFlsg-and
bioactive
study we demonstrate
of VEGFzoh mRNA
1 cells. Selective fication
af rhe cellular
mast cells produce
mRNA
of five different
in the tissues of the adorn&urn,
level. In the present pression
THE
Beate M. Hew
Char&Virchow
(V&F)
that lead m the production
show that human
IN
Krtieer-Krasaeakes.
of Dermatology,
died the most are VEGFlds and VEGFlzl. be detected
Sabine
VECiFzo6
Germany.
endothelial
cing processes VEGFm.
Andreas
OF
blot ana-
this result at
that human mast cells are a end that the expression
cell activation.
of
DlSTRlBUTlON OF .S,GNALTRANSWCTlON ELEMENTS IN ANIGEN PRESENTING CELLS FOLLOWlNG STIMULATION WrrH A CONTACT SENSTnZER. Pie Brend. Svbille Plochmann.JoechimS&me. JOmenKnor, andDeUef Becker. Departmentof Dermatology, Universityof Mainz.Mainz.Germany Based on our formal findingthat tymsine phosphodationis an eadyeventduringactivation of APC by contad sensit&zr$ we studiedthe influenceof e strong haptenon the quantityand lxatin of several ~mportent elementsof signaltransductionmechanisms. The emoUntof PKC-&II, MAP kinase~38, lyn. NF-kappa6end phosphotyroeine (pty) in humenmonocytesunder stimulation wkh M’ZVMI.benzalkonklmch,orkJeand hydrcgenperoxtie was determinedusingspetic anhbe&s andflow cytometrictechniquerafter permeabil+ z&ion of cell membraneswith seponin.In parallelthe iltre~~,,~,er ,oc~tin of these stn&t~res was analyzedbyfluorescencemicroscopy. A constlutiily hkh erpressbn of /fl and PKC-&II but low amountsof ~38. NFskappaBes well 85 ptyrwere foundh unheatedcells. Followhg etimuletbnwith the etmngcent&se”* tier MCVM,for 15 min. increeeedbindingof speck entibodieewes foundin patiiularfor ~3.3. NF-kappa8and ptyr. Morphologicalanalysismnrimwd Ls ,i,ding end revealede pronounced concentratin of ~38. NF-~~FQ~B.&‘n andPKC-Dll into aggregatesafter stimulationwith MCVMI.The presenceof the PTK inhibitortyrphOstkk BSS Cempletelyblockedthe hcreese in tyrosine phosphoryletionbut wes unableto Preventthe upregulationor translocatin of the other etructuree.Neithersuhtoti nor todc concentretbnsof the irrkati benzalkoniumdllorkfe nor ometive stress employinghydrogenpemldderesembledVie changes0bseNed ablerstimulalbn wkh MCUM,. Our datasuggest that s&era, sylna, transdutibn mecheniSmsm,ghtbe inwIved in the atih vationof APC by haptens.This activationcan not he eplained by tati effects nor responselo otietive stress Increasedform&on of p-tyris part of vlis mechanismbut seems not to contml Ihe regulationof the struclures studiedin this presentation.
ESDR I JSID I SID Abstracts
0910
0907
PSORIATICKERATINOCYTES SHOW REDUCED STAT-la AND IRF-1 ACTIVATION
AUTOCR,NE GROWTH FACTORS FOR EPIDERMOID CARCINOMA CELLS. & Meaner. U. Zinmfer. C. Hofmann and I. Norpauer, Department of Dermatology, Umversity c#Fmiburg, Germany. The CXC-chemokkms Grea and ieterleukin-8 (IL-Q stimulate the growh of melanoma cells and the ehemaaxis of neutmphils via the IL-8 receptor 0 (ILSRP). Recently high CXC-ehemokine immunoreac&y was detected in the lexms of pmlifemtive skin dwxden such as kerateaeanthoma and sqeanwus cell carcinoma. To &cidete the functional relevanceofthese fmdingsthe expreexm Grcu, IL-8 and the IL-SRP as well as their funetmnal i~nolwmmt in the proliferation response were aealysed in normal keratinozytes @+K) end in the tmnsfonned keratinccyte (TK) cell hem HaCaT, KB and A431. Semiquantitative RT-PCR and ELISA revealed vay low ecmstitutive mRNA exprerrim and protein secretion of both CXC-ehemokines in NK, whereas IO- to 100~fold higher levels were de&xl in TK. Flow cytemetric measuranents showed high expreasim ofIL-8Rb in TK, but no expression in NK. ‘Ihis tinding was corroborated by receptor mRNA assamat wkh semiquantitativs RT-PCR and analysis of II&Q promoter activity by CAT-assay showing markedly increased saady-state levels of IL-SRp mRNA as well es trenscription aaivity in TK, but not hr NK. Pmbferatmn of TK, but nd of NK, could be induced by CXC-chemekines. Canstitutive molifbration OCTK could be inibii bv neetralizin~ antibodies against the CXC&es or against IL-8RP. These studies indxate that comtitetwe b-anscripttcmally~gul& IL-SRp expissioo induces a CXC-ehemokine autwiee loop in TK supportinggrowth. mis finding eught o&r new implicatiaw for the dwelcpmaa oftherapeutic appreaches in tmnsfbrmed kemtinocyter.
IN RESPONSE
TO 1FN-y. M&any
Jackson.
Sarah
EM.
Howle*.
Rl$;ar;r:,
Weller, Elizabeth Sobln*, John A.A. Hunter. and Roddie C K I Departments of Dermatology and *Pathology. Unlverstty of’ Edinburgh: Edinburgh, Scotland. Psorlasls Is a ChronlC lnnammatory dermatosls characterlsed by hyperprollferatlve keratlnocytes (KC) which fall to terminally differentlate. The lesions are lnflnrated by IFN-y-secreting mononuclear cells which help maintain the pSOr,atlc phenotype. In normal KC, IFN-y Is a potent lnhlbiior of prollferat&I and modulator of squamous dlfferentlatlon. Slgnalllng via the IFNy receptor. and subsequent gene Induction, Involves actlvatlon of the transcrlptlOn faCtOrsSTAT-laand IRF-I, cuhnlnating In the blndlng of IRF-1 to the prOmOterS of IFNy-lnduclble genes. We sought to determlne whether there Is a defect In the response of psorlatlc KC to FN-y, which could explain the KC hyperproHferatlon In the IFNy-rich plaque. Cultures of normal adult and psorlotlc KC were established and stimulated with IFN?. Transcrtptlon fact01 aCtlVation was quantltoted by gel mobility shfft assay and autoradlography. In both normal and psorlEltlc KC, STAT-la actlvatlon was maximal 15M min. after stknulatlon; the kinetics were slmlkx. however, the pSorlatlC KC showed Smclller Increases In STAT-ICI actlvatlon after 10 min. (p=O.o37) and 15. 30, and 60 mk-!. (pe0.M. n=5). At 60 mln, STAT-la aCtlvatlOn increased by 71.fold in normal KC compared with 31-fold In p.XX,atlC KC. The decreased magnitude of STAT-la actlvatlon was followed by decreased IRF-1 actlvatlon, maximal after J-Bh. Normal KC showed a 6fold Induction. whereas IRF-1 acttvatlon in psorlotlc cells was only 2.7-fold. This lack of responsiveness to 1FN-y lndtcates a tundamental defect In the growth and differentlatlon control of psorlatlc KC, In the absence of other cell types.
of
0908
0911
GROWTH FACTOR+ (TGF-P) IS NOT INVOLVED IN GROWTH INHIBITION OF HUMAN KERATINOCYTES BY la, 25(OH),D,. A STUDY WITH ADENOVIRAL VECTOR EXPRESSING A TRUNCATED TGF-p TYPE II RECEPTOR (AdexCATpTR). Yasu$hi Hanakawa. Yujj Shirakata. Kensi Yamasaki. Koii Sm Hikaru Ueno’. and Koii Hashimoto. Dept of Dermatology Ehime University School of Medicine,Ehime, Japan, *Dept. of Cardiology Kyushu University School of Medicme, Fukuoka, Japan. la, ‘IT-Dlhydroxyvitamin Da(1a, 25(0H),D& an active form of vitamin D,, inhibits the growth of normal human keratlnocytes (NHK). An involvement of TGF-p, an autocrine growth inhibitor for NHK, is proposed, although it is still controversial because of difficulty to block TGF-p activity in NHK. To solve this problem, we constructed an adenoviral vector (Adex) expressing a truncated TGF-p type II receptor (TBTR) with a dominant negative effect, which blocks TGF-6 slonal transduction. NHK was cultured in serum-free MCDB153 medlbm and DNA synthesis was measured by bromodeoxyuridine Incorporation. A 90 minute infection with AdexCAT@TRat 5 m o i. (multiplicity of InfectIon) induced an expression of TBTR in NHK after 24 h, confirmed by immunoblot and immunostaining, and abolished the growth inhibitory effect on NHK of TGF-61 at 0.1 to 5 ng/ml completely. An addition of 1O-6M of la, 25(OH),Dsto NHK infected with 5 m.o.i of AdexCATbTR and Adex (control vector) reduced DNA synthesis to 59.3% and 62.2% at 6 h, 24.1% and 31.8% at 12 h, respectwely. Since 10, 25(OH),D,inhibits the NHK growth regardless of prevention of TGF-p signal transduction. TGF-P is not involved in the growth InhibItion of NHK by la. 25(0H),Dz
COLLAGENASE-3 (MMP-13) EXPRESSION BY SQUAMOUS CELL CARCINOMA CELLS IS DEPENDENT ON THE ACTIVITY OF p38 MI,TOGEN A;$ATED PROTEIN IUNASE. Nina G~eman*. and Maw Ktih&ri, Depts. of Dermatology and *Gtorhinolaryngology, University of Turku. Finland. ~ollagenase-3 (MMP-13) is a new matrix metallopmteinase (MMF’), which is specifically expressed by transformed keratinccytes, i.e. HaCaT cells and tumor cells of invasive squamous cell carcinomas (SCCs) of the head and neck in culture and in viva. We have elucidated the molecular mechanisms of enhancement of hlMF-13 expression at mRNA and pm&in level by tomor necrosis factor-a (TNF-a) and transforming growth factor+ (TGF-p) in HaCaT cells and in cell lines from cutaneous and oral SCCs. In both HaCaT and SCC cells TNF-a and TGF-!3 rapidly and transiently activate hvo distinct mitogen activated pmtein kinases (MAPKS): extracellolar stimulus-regulated kinase (ERK)l,Z and ~38 MAPK. In addition, TNF-a activates Jun N-terminal k&se. Treatment with SB 203580, a selective inhibitor of ~38 MAPK entirely abrogated the. induction of MMP-13 expression by both TNFa and TGF-fl and also inhibited basal expression of MMP-I3 by HaCaT and SCC cells. In addition, SB 203580 abrogatedthe stimulation of collageruse(MMP-1) expression by TGF-fl and TNF-a and entirely inhibited release of collagenolytic activity to culture media in response to TNF-a and TGF-p. Inhibition of MAPK pathway Raf/MBKl/ERKl,2 by PD 98059, a specific inhibitor of MF,Kl activation also partially prevented stimulation of MMP- 13 expression by TGF-B, but not by TNF-a. These results show that activation of both MM&I3 and MMP-I expression in transformed keratinocytes by TNF-a and TGF-p requires activity of ~38 MAPK, indicating that specific inhibition of this pathway may provide a novel way to combat invasion and metastasis of SCC cells.
0909
0912
TRANSFORMING
ACTIVATION-DEPENDENT
EXPRESSION
MAST
Griitzkau.
CELL LINE,l.
&nnelie
Mtiller.
University,
Balm,
Vascular
Departments
lization
growth
factor
VECiF,m,
VEGF,,sor
VEGF,m,
of these isoforms
VEGFII,,
HUMAN
Clinic, Humboldt
VEG&,and
VEGFII,.
lysis of the conditioned
the protem level. In summary, source of the strong heparin
leukemic
Vay
recently,
mast cell line-l expressed
was a&wed by sequence
thus study provides
VEGFzw m these cells is dependent
that have been stu-
VEGF at the mRNA
of stimulated
bmdlng
spli-
isoforms,
VECiFzos mRNA
could
HMC-1
on appropriate
by RT-PCR.
while
by HMCThe amph-
Western
cells confumed
evidence
de nova ex-
(HMC-I),
and released
analysis.
growth factor VEGF,,
we could
and at the protein
for the first time the stimulated
was verified
medium
The &forms
level is unknown.
of VEGF*,x mRNA
expected
alternative
homodimeric
the kidney and the heart, the exact loa-
VEGF,89 were constitutively
detection
of the product
in the human
undergoes
While VEGFlsg-and
bioactive
study we demonstrate
of VEGFzoh mRNA
1 cells. Selective fication
af rhe cellular
mast cells produce
mRNA
of five different
in the tissues of the adorn&urn,
level. In the present pression
THE
Beate M. Hew
Char&Virchow
(V&F)
that lead m the production
show that human
IN
Krtieer-Krasaeakes.
of Dermatology,
died the most are VEGFlds and VEGFlzl. be detected
Sabine
VECiFzo6
Germany.
endothelial
cing processes VEGFm.
Andreas
OF
blot ana-
this result at
that human mast cells are a end that the expression
cell activation.
of
DlSTRlBUTlON OF .S,GNALTRANSWCTlON ELEMENTS IN ANIGEN PRESENTING CELLS FOLLOWlNG STIMULATION WrrH A CONTACT SENSTnZER. Pie Brend. Svbille Plochmann.JoechimS&me. JOmenKnor, andDeUef Becker. Departmentof Dermatology, Universityof Mainz.Mainz.Germany Based on our formal findingthat tymsine phosphodationis an eadyeventduringactivation of APC by contad sensit&zr$ we studiedthe influenceof e strong haptenon the quantityand lxatin of several ~mportent elementsof signaltransductionmechanisms. The emoUntof PKC-&II, MAP kinase~38, lyn. NF-kappa6end phosphotyroeine (pty) in humenmonocytesunder stimulation wkh M’ZVMI.benzalkonklmch,orkJeand hydrcgenperoxtie was determinedusingspetic anhbe&s andflow cytometrictechniquerafter permeabil+ z&ion of cell membraneswith seponin.In parallelthe iltre~~,,~,er ,oc~tin of these stn&t~res was analyzedbyfluorescencemicroscopy. A constlutiily hkh erpressbn of /fl and PKC-&II but low amountsof ~38. NFskappaBes well 85 ptyrwere foundh unheatedcells. Followhg etimuletbnwith the etmngcent&se”* tier MCVM,for 15 min. increeeedbindingof speck entibodieewes foundin patiiularfor ~3.3. NF-kappa8and ptyr. Morphologicalanalysismnrimwd Ls ,i,ding end revealede pronounced concentratin of ~38. NF-~~FQ~B.&‘n andPKC-Dll into aggregatesafter stimulationwith MCVMI.The presenceof the PTK inhibitortyrphOstkk BSS Cempletelyblockedthe hcreese in tyrosine phosphoryletionbut wes unableto Preventthe upregulationor translocatin of the other etructuree.Neithersuhtoti nor todc concentretbnsof the irrkati benzalkoniumdllorkfe nor ometive stress employinghydrogenpemldderesembledVie changes0bseNed ablerstimulalbn wkh MCUM,. Our datasuggest that s&era, sylna, transdutibn mecheniSmsm,ghtbe inwIved in the atih vationof APC by haptens.This activationcan not he eplained by tati effects nor responselo otietive stress Increasedform&on of p-tyris part of vlis mechanismbut seems not to contml Ihe regulationof the struclures studiedin this presentation.